174. POSTEROMEDIAL CORNER INJURY PATTERNS IN TRAUMATIC KNEE DISLOCATIONS

Abstract

Purpose: Traumatic knee dislocations are complex injuries. A thorough knowledge of the pattern of ligament damage is essential to plan for definitive treatment. Injuries to the structures of the posteromedial corner (posterior oblique ligament, the semi-membranosus tendon and its expansions, the meniscofemoral and meniscotibial ligaments, posterior horn of the medial meniscus and posterior reflections of the deep and superficial medial collateral ligament) can contribute to rotational laxity and have not been previously described in the setting of knee dislocations. We set out to evaluate the injury patterns of the posteromedial corner in a series of traumatic knee dislocations.

Method: A radiographic (MRI) study was conducted on 22 multi-ligament knee injuries in 22 patients, managed at a level one trauma centre by a single surgeon between July 2006 and May 2008.

Results: There were 14 male and 6 female patients with an average age of 29. The mechanism of injury was high velocity in 10 cases, and low velocity in 12 cases. One case (ACL/PCL/posterolateral corner injury) was associated with a vascular injury. While the incidence of MCL injury was 59%, injury specific to the PMC was evident on MRI in 81.8% (18/22) of cases. The deep and superficial MCL were involved in 13/18 and 12/18 PMC injuries, respectively. The posterior oblique ligament was injured in 11/18 cases and the semi-membranosus and its expansions were injured in 10/18 cases (all distal). Injuries to the posterior horn of the medial meniscus (9/18 cases) were associated with a tear of the menisco-femoral/meniscotibial ligaments in all cases.

Conclusion: Injury to the PMC was common with high-grade multi-ligament knee injuries in this series. PMC injuries were more common than MCL injuries alone. Injury to the posterior horn of the medial meniscus was predictive of more extensive PMC injury in all cases. The posteromedial corner of the knee is an under recognized area where important injuries can occur in the setting of a dislocatable knee. Future research will involve the correlation of the injury patterns described in this series to clinical measures of knee instability and laxity.